Abstract

Green synthesis represents an eco-friendly alternative to the environment by minimizing the use of chemical reagents and reduces temperature and pressure conditions. Thuja orientalis has a wide medical use because it contains a large amount of compounds derived and was decided to use for the synthesis of nanoparticles. Leaf extract was obtained and characterized by Infrared Spectroscopy Fourier Transform (FTIR) observed carboxyl groups (-C=O), hydroxyl (-OH) and aromatic amines (-NH), then proceeded to the synthesis of nanoparticles, using AgNO3 as precursor at a concentration of 15 mg L-1, obtaining AgNPs was verified by observing the Ultraviolet-visible Spectroscopy (UV-Visible) absorbance characteristic plasmon between 410-420 nm which reveals the reduction of silver ions (Ag +) into metallic silver (Ag0), the aqueous solution was characterized by scanning electron microscopy (SEM) nanometric sizes observed. The particles obtained were stable for 4 months in aqueous solution, where the characteristic plasmon absorbance was observed by UV-visible spectroscopy for this time.

Keywords: Green synthesis; Thuja orientalis; Silver; Nanoparticles

Keywords

Green synthesis; Thuja orientalis; Silver; Nanoparticles

Introduction

Nanomaterials may provide solutions to technological and
environmental challenges in the areas of solar energy conversion,
catalysis, medicine, and water treatment [1]. The noble metals,
especially silver and gold, have attracted great attention due to their
innumerable applications in various branches of science, namely
catalysis, photonics, photography, chemical sensing, and most
importantly, in the medicinal field antimicrobial agents [2].
Colloidal silver is of particular interest because of its distinctive
properties, such as good conductivity, chemical stability, catalytic
and antibacterial activity. Generally, metal nanoparticles can
be prepared and stabilized by chemical, physical and biological methods; the chemical approach, such as chemical reduction,
electrochemical techniques, photochemical reduction [1] and
pyrolysis and physical methods, such as Arc-discharge and
physical vapor condensation (PVC) [3].

Most of the chemical methods used for the synthesis of
nanoparticles are too expensive and also involve the use of toxic,
hazardous chemicals that are responsible for various biological risks.
This enhances the growing need to develop environmentally friendly
processes through green synthesis and other biological approaches.
Sometimes the synthesis of nanoparticles using various plants
and their extracts can be advantageous over other biological
synthesis processes which involve the very complex procedures
of maintaining microbial cultures [4]. Many of such experiments
have already been started such as the synthesis of various metal
nanoparticles using fungi like Fusariumoxy sporum [5], Penicillium
sp [6]. But, synthesis of nanoparticles using plant extracts is
the most adopted method of green, eco-friendly production of
nanoparticles and it also has a special advantage that the plants are
widely distributed, easily available, much safer to handle and act
as a source of several metabolites [7]. There have also been several
experiments performed on the synthesis of silver nanoparticles
using medicinal plants.

With the advent of advance technologies and improved scientific
knowledge, a way for research and development has been paved in
the field of herbal and medicinal plant biology towards intersection
of nanotechnology. One such interference is employing plants in
synthesis of nanoparticles. The possibilities of employing plants in the
synthesis of nanoparticles have burgeoning interest as an important
source against reliable and environmentally benign method of
metallic nanoparticles synthesis and it is characterization [8].

Studies have shown that the size, morphology, stability and
properties (chemical and physical) of the metal nanoparticles are
strongly influenced by the experimental conditions, the kinetics
of interaction of metal ions with reducing agents, and adsorption
processes of stabilizing agent with metal nanoparticles. Hence,
the design of a synthesis method in which the size, morphology,
stability and properties are controlled has become a major field of
interest [9].

Taxonomy and chemical constituents of Thuja orientalis

Thuja orientalis is a tree distributed spread widely in Japan,
China and Korea [10], this it belongs to the family of Cupressaceae,
Subfamily Cupressaceae, and genera Platycladus have a big quantity
of synonymy. It is an evergreen coniferous tree, used in landscape, his
cup is narrow in its early years and increases as ages, the general shape
is conic and the branches have a laminar form [11]. The branches
are fan-like in it is final extreme and upwardly disposed. Branches
and leaves have a flat form. The leaves are squamiforms, it means,
everyone are like a squama, disposed one on other in an alternated
way, they are imbricated. The leaves have a well-marked tip disposed
in opposite way. Towards the tip, every branch changes from deep
green to green yellowish color.

It is a dioic tree, the female cone is whitish or rose pale and later
bluish-green, with tips well marked and open like spikes, each one of them are a squama and have 6-8 of flattened oval form, are thick and
provided with an apical hook, the cone is dehiscent when becomes
to maturity then it becomes brownish-tan. Every cone has about 6
seeds, ovoid-trigonoidas and is released generally wingless [11]. The
leaves have essential oils which are used in traditional medicine as
antifungic, bactericide and other properties such as treatment of
cancer, eradicate parasitic worms, and many others. Normally
the oil is toxic, mainly for the presence of α- thujone. The other
compounds of the leaves are; rhodoxanthin, amentoflavone,
hinokiflavone, quercetin, myricetin, carotene, xanthophylls and
ascorbic acid [12].

Materials and Methods

Materials

All the chemicals and reagents used in this study were of analytical
grade. All glass wares were washed in dilute HNO3 acid and rinsed
thoroughly with distilled water prior to use and dried.

Sample collection

Thuja orientalis, the specimen is relatively common as it is used
as ornamental shrub, previously the work of taxonomic identification
of the species was once defined, and we proceeded to the selection
of leaves to obtain the extract. The main parameters to consider for
collection are: young leaves, in good condition, with no evidence of
disease or pests. They were then washed with tap water and then with
deionized water, then were weighed and the leaves were cut into thin
parts removing the stems.

Obtaining the extract

Was weighed 5 g of finely chopped leaves into a flask with 100
mL of deionized water and brought to a temperature of 80-85°C, the
mouth of the flask was capped to prevent evaporation losses, plant
sample remained a period of 15 minutes, this time completion was
removed and allowed to cool for 5 minutes, the mixture was filtered
with whatman 40 filter paper and stored in amber bottles at low
temperature for subsequent use.

Synthesis of AgNPs

AgNPs synthesis was performed with 50 mL of Thuja orientalis
extract at a temperature of 80°C with constant stirring, adding 10 mL
of AgNO3 at different time intervals for each of the concentrations
(1, 10 and 15 ppm) , UV-vis spectroscopy to corroborate obtaining
AgNPs was used, changes in the different variables (temperature,
stirring, coloration change) were recorded, the synthesis was
completed within 30 minutes from being started, a change was
observed to be yellow to amber as shown in Figure 1, the samples
were refrigerated for later analysis.

Figure 1: Difference in color between the extract before and after performing the synthesis. A) Extract, B) after adding 10 mL of 10 ppm AgNO3 in a time of 30 minutes.

Characterization techniques

The leaf extract Thuja orientalis was characterized by Infrared
spectroscopy Fourier transform (FTIR) to identify key functional
groups of biomolecules present, the synthesis of silver nanoparticles
visual observations of color changes were made during the
development of the synthesis, then samples were analyzed by
spectroscopy Ultraviolet-visible (UV-Vis) to determine the
absorbance characteristic plasmon of the nanoparticles, then the
nanoparticles obtained were characterized by scanning electron
microscopy (SEM) to determine morphologies and sizes of the
particles present in the solution.

Results and Discussion

FTIR spectroscopy

The sample for FTIR analysis was prepared with chloroform
extract, the analysis results are shown in Figure 2, where major
functional groups present in the extract were identified and associated
with the following wavelengths at 2432 cm-1 for NH- and OH groups
at 2921 cm-1 for -CH2-, at 2851 cm-1 CH=CH2 and O in 2347 cm-1 is
attributed to O=C-OH at 2065 cm-1 was associated with CO-CRN2 in
1773 cm-1 for C=OR, in 1635 cm-1 and HC=CH-NH2, in 1463 cm-1 for
CH2 and -CH3- in 1377 cm-1 for O-CO-CH2, at 1315 cm-1 for C=O-Φ-
OH and NH, in 1057 cm-1 to C-OH groups at 873 cm-1is attributed to
SO, at 762 cm-1 for -NH2 and -NH-, and finally 538 cm-1 is attributed
to C-Cl.

Figure 2: FTIR Spectrum of the leaf extract Thuja orientalis.

UV-visible Spectroscopy

At the time that a molecule absorbs UV-Vis radiation, the
absorbed energy excites electrons from lower energy orbitals to
orbitals of higher energy. The UV-Vis maximum absorption occurs
at a given wavelength characteristic of the molecular structure
can be determined and a graph of intensity versus wavelength
absorption. The position and shape of the surface plasmon band
depends on the size and shape of the particles, because if these
increase, the absorption band tends to shift towards longer
wavelengths with higher [13] sizes. The AgNPs have absorbance at
a characteristic wavelength between 300 and 800 nm [14], greater
absorbance within the range of 460 and 540 nm are attributed to
sizes of 10 to 30 nm [15].

The results obtained for the synthesis with AgNO3 to 1, 10 and
15 ppm with the extract are shown in Figure 3, 4 and 5, where the
maximum plasmon absorbance varies ranges between 403 and 425
nm.

Figure 3: Surface plasmon spectra after the addition of different concentration of metal ion silver with 10 mL of AgNO3 to 1 ppm, A) At the time of synthesis, B) Analysis obtained 4 months after having performed the synthesis.

Figure 4: Surface plasmon spectra at different concentration metal ion concentration with 10 mL of 10 ppm AgNO3, A) At the time of synthesis, B) Results obtained 4 months after completing the synthesis.

Figure 5: Surface plasmon spectra at different concentration metal ion concentration with 10 ml AgNO3 15 ppm A) At the time of synthesis, B) 4 months after synthesis has been made.

For synthesis with AgNO3 to 1 ppm, a gradual increase in
absorbance ranging from 0.04 to 0.15 units, because the increase
in absorbance is minor to observed, this in a small amount of
nanoparticles obtained is attributed since the plasmon absorbance
appears in length range characteristic wave, reported in the literature
for silver nanoparticles. After four months of having made the
synthesis, the samples were reanalyzed, the results show that for
the times 1 and 2, no longer the plasmon characteristic absorbance
seen, this might be due to the agglomeration of nanoparticles in the
solution.

In Figure 4, the results of synthesis are shown in AgNPs a solution
to 10 ppm of AgNO3

Plasmon absorbance between 409 and 420 nm which is attributed
to nanometer-sized particles can be seen. Furthermore, when the same
solution was analyzed four months after synthesis as seen in Figure B,
there was an increase in absorbance which can be attributed to it being
cooling the continuous solution reacting and plasmon absorbance
are observed between 415 and 420 nanometers, which shows that
the synthesized nanoparticles remain stable, it is noteworthy that no
precipitates are present in the flasks.

In Figure 5, the results of synthesis are shown AgNPs with a
solution of AgNO3 at15 ppm

The results observed in the plasmon absorption between 403
and 415 nm at the time of synthesis, are attributed to the particles of
nanometric size according to that reported in the literature; after 4
months of having made the synthesis, the evolution of nanoparticles
in solution was analyzed, results shown in Figure B, and found that
the absorbance remains with nanometric sizes, it is noteworthy that
by this time small precipitates in the solution began to be observed, so it had to be filtered to be analyzed, precipitation is attributed to the
agglomeration of nanoparticles.

SEM characterization

To determine the morphology of the synthesized AgNPs sample,
they were observed with scanning electron microscopy. The sample
analyzed for scanning electron microscopy, in which the synthesis
was 10 ppm of AgNO3 was used, the microscopy analysis were
performed 40 days after the synthesis, and those samples that showed
no precipitates, the results are shown in Figure 6.

Figure 6: SEM micrograph obtained 40 days after synthesis.

In micrograph spherical shapes of nanoparticles, some particle
sizes of 100 nm are observed, the solutions are analyzed that showed
no precipitates, the greater sizes observed 100 nanometers are
attributed to agglomeration of the nanoparticles obtained, since
these remained in solution, since the time between the synthesis and
characterization by microscopy time it was about 4 months.

Conclusions

The synthesis by green chemistry AgNPS present satisfactory
results for the species Thuja orientalis, so it is enhanced as a species
for this type of synthesis, for which the data obtained by UV-visible
spectroscopy showed the typical plasmon absorbance for silver
nanoparticles (between 403 and 420 nm) sizes at the synthesis are in
the nanometer range; the obtained nanoparticles tend to agglomerate,
but observed by SEM showed spherical morphologies within the
range of 100 to 200 nm, these sizes may vary significantly since
the sizes depend on the type of mechanism used for the synthesis,
precursors and conditions reaction.

Acknowledgments

The authors thank Universidad Tecnologica de Tulancingo for the
facilities provided for the realization of this research.